1. Field of the Invention
The present invention relates to a detecting apparatus and a detecting method of detecting the housing state of a substrate.
2. Description of the Related Art
In a photolithography step in manufacturing process, for example, of a semiconductor device, for example, a resist coating treatment of applying a resist solution onto a semiconductor wafer (hereinafter, referred to as a “wafer”) to form a resist film, a developing treatment of developing the resist film after exposure, thermal processing performed after the resist coating treatment and before and after the developing treatment and the like are performed to form a predetermined resist pattern on the wafer.
The series of treatment and processing is performed in a coating and developing treatment apparatus incorporating a plurality of various kinds of processing and treatment units. The coating and developing treatment apparatus usually includes a cassette station for transferring in/out the wafer to/from the apparatus, a processing station in which the various kinds of treatment and processing units are installed, and an interface section for passing the wafer to/from an aligner.
In the cassette station, a mounting table on which a cassette capable of housing a plurality of wafers can be mounted, and a transfer unit for accessing the cassette mounted on the mounting table and transferring the wafer between the cassette station and the processing station, are provided. The cassette is usually configured to be able to house a plurality of wafers at multiple tiers in the vertical direction in its casing. A door for transferring-in/out the wafer is provided in one side surface of the cassette, and a door opener for opening the door is provided on the mounting table side for mounting the cassette.
When a cassette is mounted on the mounting table, the door is opened by the door opener, and the transfer unit accesses the wafer in the cassette.
Incidentally, when the cassette housing unprocessed wafers is mounted on the mounting table, a so-called mapping operation is performed for detecting the housing states such as the presence or absence, the housing attitude and the like of the wafer at each tier in the cassette. The access position of the transfer unit to the cassette is determined based on the mapping data of the mapping operation.
This mapping operation has been conventionally performed by optically detecting the housing states of the wafer by an optical sensor. This optical sensor has been conventionally attached to a detecting apparatus provided at a position adjacent to the mounting table for the cassette. The detecting apparatus includes a supporting member for supporting the optical sensor, and the supporting member is capable of sliding in the horizontal direction by means of a horizontal moving mechanism and sliding in the vertical direction by a raising and lowering drive mechanism.
When operating the detecting apparatus, the supporting member waiting outside the door opener horizontally slides a length corresponding to the thickness of the door opener and the door of the cassette to allow the optical sensor to enter the cassette, and then the supporting member is raised and lowered to allow the optical sensor to scan the wafers aligned in the vertical direction to thereby perform the mapping operation (Japanese Patent Application Laid-open No. 2003-218018).
However, since the supporting member needs to slide the length corresponding to the thickness of the door opener and the door of the cassette as describe above for the conventional detecting apparatus, a space needs to be secured for the slide between the mounting table in the cassette station and the transfer unit. Therefore, there is a problem that the footprint increases as the coating and developing treatment apparatus increases in size, failing to effectively use, for example, the space in the clean room in which coating and developing treatment apparatus is set.